ANADARKO		PETROLEUM		CORPORATION			1201 LAKE ROBBINS DRIVE, THE WOODLANDS, TEXAS 77380

			P.O. BOX 1330		HOUSTON, TEXAS 77251‐1330			U.S.A.			PH. (832)636‐1000

February	7,	2014	 						

Mr.	Stanley	Krivo		

U.S.	EPA	Region	4	

61	Forsyth	Street,	S.W.	

Atlanta,	GA	30303‐8960	

RE: Anadarko BlackHawk and BlackHornet OCS Air Permit Application for Drilling,

Exploration, and Maintenance Activities in the Eastern Gulf of Mexico

EPA’s Follow up Comments in Email Dated January 16, 2014

Dear	Mr.	Krivo:	

EPA	Region	4	provided	follow‐up	comments	via	email	on	January	16,	2014	to	the	responses	submitted	

by	Anadarko	Petroleum	Corporation	(Anadarko)	in	November	2013.		This	letter	addresses	the	follow	up	

comment	no.	19.		The	other	comments	were	addressed	in	a	separate	submittal.	

Modeling

Project Emissions

19. Provide	reason	the	impact	assessment	using	a	single	supply	boat	is	appropriate	given	

simultaneous	operation	of	multiple	supply	boats	is	planned.	

The	total	fuel	limit	provided	for	all	utilized	supply	boats	is	provided	as	justification.		The	

emissions	from	the	modeled	supply	boat	was	indicated	to	be	based	on	the	proposed	fuel	limit	so	

the	impact	modeling	properly	represents	the	impacts	from	one	or	more	supply	boat	operations.	

The	fuel	limit	for	the	all	supply	boats	is	based	on	24‐hour	and	annual	periods.		Considering	the	

short	term	standards	(e.g.	1‐hour	NAAQS),		the	only	way	the	modeled	single	supply	boat	would	

represent	the	worst‐case	supply	boat	impact	would	be	if	the	fuel	limit	included	an	hourly	value	

and	the	emissions	used	in	the	modeling	were	based	on	the	hourly	fuel	limit	consumed	by	the	

single	boat.	

The	application	indicates	the	shortest	period	for	supply	boat	fuel	limit	was	24‐hours.		Multiple	

supply	boats	could	operate	under	the	24‐hour	fuel	limit,	although	not	for	the	full	24‐hours	

period,	producing	larger	hourly	emissions	and	greater	impacts	than	that	associated	with	a	

single	boat.	
Mr.	Krivo	

Page	2	of	2	 	 	

Anadarko Response:			

The	typical	supply	boat	operating	scenario	consists	of	one	supply	boat	in	transit	and	one	or	two	

supply	boats	near	the	drillship	transferring	fuel	and	equipment	at	any	given	instance	during	the	

proposed	project	activities.		Hence,	one	supply	boat	was	modeled	at	25	nautical	miles	from	the	

drillship	in	the	direction	of	the	nearest	receptor	and	other	supply	boats	were	assumed	to	be	

near	the	drillship	for	air	dispersion	modeling	analysis.	

The	historical	supply	boat	fuel	usage	data	shows	that	one	supply	boat	consumes	maximum	of	

100	barrels	of	fuel	in	a	day.		Hence,	Anadarko	conservatively	requested	maximum	daily	fuel	limit	

of	200	barrels	per	day	to	cover	simultaneous	operations	of	two	or	more	supply	boats.		The	

historical	supply	boat	fuel	usage	data	also	shows	that	the	supply	boat	consumes	higher	amount	

of	fuel	(i.e.,	approximately	4.5	barrels	per	hour)	when	in	transit	carrying	load.		On	the	other	

hand,	the	same	supply	boat	consumes	significantly	less	fuel	(i.e.,	approximately	1.75	barrels	per	

hour)	when	it	is	near	the	drillship	for	transferring	equipment	and	fuel.			

Based	on	the	prior	experiences	with	the	similar	projects,	Anadarko	performed	a	short‐term	air	

dispersion	modeling	based	on	the	emissions	resulting	from	the	expected	worst‐case	short–term	

supply	boat	fuel	usage	of	8.33	barrels/hour.		Note	that	8.33	barrels/hour	fuel	consumption	

represents	the	worst‐case	total	fuel	consumption	for	all	the	supply	boats	within	25	nautical	

miles	of	the	drillship.		As	explained	above,	the	expected	worst‐case	short–term	supply	boat	fuel	

usage	of	8.33	barrels/hour	adequately	covers	fuel	requirements	for	one	supply	boat	in	transit	

and	two	supply	boats	performing	transfer	operations	near	the	drillship.	

In	order	to	represent	the	conservative	scenario,	the	proposed	air	dispersion	modeling	

methodology	assumes	that	the	emissions	from	all	the	supply	boats	(i.e.,	emissions	generated	by	

the	total	supply	boat	fuel	consumption	of	8.33	barrels	per	hour)	would	be	released	at	25	

nautical	miles	from	the	drillship	in	the	direction	of	the	nearest	receptor.		Hence,	a	point	source	

was	placed	at	25	nautical	miles	from	the	drillship	in	the	direction	of	the	nearest	receptor	to	

represent	the	supply	boat	in	transit	and	assumed	that	short‐term	emissions	from	all	supply	

boats	were	released	at	this	location.	

Hence,	Anadarko	believes	that	the	short	term	emissions	and	the	proposed	air	dispersion	

methodology	represent	the	worst‐case	impact	assessment.	

Please	do	not	hesitate	to	contact	Mr.	Rahul	Pendse,	Trinity	Consultants	at	(225)	346‐4003	or	Ms.	Sara	

Carlson,	Anadarko	at	(832)	636‐1273	if	you	have	any	questions	or	require	additional	information.